There is already much information readily available in relation to circuitry for mobile telecommunications, particularly in relation to mobile telephony.
One problem particularly associated with mobile telephony antenna circuitry design relates to the ability of such circuitry to pass various tests so that it meets internationally approved standards in relation to a number of criteria. One of those criteria is the so-called “blocking test”. In this test, transmitting circuitry is tested in the presence of a high power blocking signal in order to simulate a situation where two people are operating simultaneously mobile communication devices using different networks, one of which is emitting at a full power (as it is far away from its base station), and the other emitting at minimum power level. Whilst in some circumstances the need to pass this test can propose considerable design constraints on transmitter circuitry, for the reasons set out below, for some data modulation formats the very nature of the modulation format makes this blocking problem a less important one. For example, current GSM telephones generally operate using GMSK data format which has a constant amplitude envelope for its transmitted signal, meaning that the separation between any received blocking signal and the intended transmitted signal is always large enough in terms of amplitude. This means that the received “blocking” signal is of a level which does not affect the power control stability of the signal sent to the antenna.
However, it has recently been proposed to employ an enhanced data format with the GSM system. This enhanced system, known as “EDGE” (enhanced data GSM environment) differs in terms of signal characteristics in many ways compared to GMSK formatting. Whilst EDGE has advantages, in terms of increased data transmission rates and efficiency of use of the GSM spectrum, it does result in a transmitting signal which is of varying amplitude envelope. Accordingly, in this situation, there are certain occasions when the signal output by an antenna employed with an EDGE format transmitting device will be relatively low, particularly in relation to any adjacent signal being transmitted at high power. This can result in instabilities being generated in the transmitting circuitry of a device employing the EDGE format, leading to breakdowns in transmission, as well as the potential for circuitry damage in extreme circumstances.